Work machines often include various auxiliary systems, including but not limited to, air conditioning systems, hydraulic systems and heating systems. These auxiliary systems are typically belt or gear driven systems powered by an engine. Thus, the speed at which the engine operates dictates the power delivered to the auxiliary system. Often, the engine is operating at speeds that produce and deliver more power than needed to the auxiliary systems, resulting in wasted energy.
However, engineers have developed electrically-powered auxiliary systems, such as the auxiliary systems shown in U.S. Pat. No. 5,963,020, issued to Orr, on Oct. 5, 1999. In the Orr work machine, mechanical power created by the engine is transferred to a generator system via a drive train. The generator system converts the mechanical power to electrical energy, and supplies the electrical energy to various auxiliary systems within the work machine. Unlike with the mechanically-powered auxiliary systems, the amount of energy supplied to the electrically-powered auxiliary systems can be controlled by the generator system. Therefore, electrically-powered auxiliary systems, such as the heating system, can often be operated more efficiently. Although the Orr method provides electrical energy on demand to auxiliary systems when the engine is operating, the method does not address providing electrical energy to the auxiliary systems when the engine is inactive.
There are situations in which it is desirable to operate an auxiliary system while the engine is inactive. For instance, over-the-road truck operators often spend the night in a cab of the truck during multiple-day trips. During cold weather, the operator will need to heat the cab overnight. Typically, the operators idle the engine to utilize the conventional heating system powered by the engine, or connect the truck to an auxiliary power unit, or shore power, to power an alternative heating system, such as an electric heater. When the engine is idling, the truck is consuming fuel and creating exhaust, resulting in a decrease of fuel economy and an increase in undesirable emissions. When using the alternative heating system, the auxiliary power unit must produce a considerable amount of electrical energy to operate the alternative heating system. Further, the operator may be required to exit the cab into the cold weather in order to connect the truck to the auxiliary power unit. Similarly, off-road work machine operators may also need to heat the cab while the engine is inactive. For instance, the operator often remains in the cab of the work machine while logging data or completing reports. Again, during cold weather, the operator will need to idle the engine or utilize the auxiliary power unit to power the alternative heating system.
The present invention is directed to overcoming one or more of the problems set forth above.